1. Field of the Invention
The invention relates to a braking structure for a tape measure, and in particular, to a braking structure for a tape measure in which a stopping piece is pressed in biased manner using the resilience force of a spring.
2. Description of the Prior Art
In a conventional braking structure for a tape measure, the essential elements thereof, i.e., the releasing key, the braking element, and the stopping piece are characterized in that they are all made of plastics and are used to clamp the tape measure without the bias of any resilience force other than that inherent in the plastics. As such, the clamping capability of the braking structure against the tape measure is insufficient. Immediately after the tape is pulled out, the user has often to move the snap key to lock the tape. Otherwise, a slight careless movement will lead to retraction of the tape at once; hence, the user himself or other person nearby may be hurt by the sudden unexpected retraction. On the other hand, in using a conventional snap key, the constant pushing open or snap fastening thereof tends to cause fatigue of its push and snap components. Further, the conventional braking structure typically is high in cost and is not easy to incorporate, in addition to being susceptible to damage.
There is, therefore, a need for a braking structure which overcomes the many disadvantages of conventional structures. The tape measure braking structure of the present invention overcomes the disadvantages of such conventional braking structures for a tape measure, introducing improvement and innovation.
An object of the present invention is to provide a braking structure for a tape measure which is biased to press against a stopping piece using the resilience force of a spring, and is thereby adapted to provide a greater breaking force for a tape measure.
These and other objects are achieved by the subject braking structure for a tape measure, which comprises an upper casing, a lower casing, a clip for wearing, a tape assembly, a release key, a braking element, a spring, a stopping piece, and a buffering piece. The stopping blocks are provided at respective tape outlets of said upper and lower casings and are provided on their top with contours that correspond to the contour provided at said stopping piece, such that the tape can be clamped therebetween to prevent retraction. A screw port is provided at the upper surface of said upper casing for fastening said clip to said tape measure.
The tape assembly is biased to retract said tape measure, and is slipped on a tape shaft protruded from said lower casing so that the user may conveniently pull and withdraw the tape. The release key, together with said braking element and said spring, constitute a push key switch between said upper and lower casings. A spring is provided on said braking element, disposed between said braking element and an end of said release key. A resilient biasing action thus results to force the braking element away from the release key.
The stopping piece is configured generally as a rectangular flat plate-shaped pushing bar and is positioned between said braking element and a portion of the tape of said tape means. One of its ends is formed with a tapered sectional surface that, in conjunction with the stopping blocks provided on the upper and lower casings, form two sectional surfaces having a clamping action upon the tape portion.
The buffer piece is formed by an elastic piece having two arc features at one end and is mounted on the peripheral side at the tape outlets of said upper and lower casings. It is positioned just beneath he tape, such that during withdrawal or retraction of the tape, it safety stops an L-shaped stopping angle at the end of the tape in buffered manner.
The braking structure for a tape measure according to the present invention incorporates a structure between the release key and the braking element in the braking structure, so as to provide a resilient braking force sufficient even for larger tape measures. Specifically, the braking structure takes advantage of the resilience force of a spring in said braking structure to push said braking element against the stopping piece, so as to capture the tape tightly and intimately against the stopping blocks provided between said upper and lower casings. This releasably fixes the tape during use.